1. Field of the Invention
The present invention provides genes, polypeptides, and expression constructs therefor, recombinant photosynthetic microorganisms and methods of uses therefor, such as the production of branched-chain alcohols, which can optionally be derivatized to produce further compounds. This biological route provides advantages over other known methods of production.
2. Incorporation by Reference of Sequence Listing
This application contains references to amino acid sequences and/or nucleic acid sequences which have been submitted concurrently herewith as the sequence listing text file “SGI1220-2_ST25.txt”, file size 25.0 KiloBytes (KB), created on Dec. 27, 2011. The aforementioned sequence listing is hereby incorporated by reference in its entirety pursuant to 37 C.F.R. §1.52(e)(5).
3. Background Information
Branched-chain alcohols and their derivatives have a variety of utilities that are known in the art, for example, as fuels, fuel additives, and solvents. Advantages of using branched-chain alcohols such as isobutanol, 2-methyl-1-butanol, and 3-methyl-1-butanol as fuels or fuel additives include an energy content higher than that of ethanol and their ability to be transported using existing fuel pipelines. Traditional methods for the production of branched-chain alcohols are costly, for example fermentation requires a fermentable carbon source, typically a sugar or polysaccharide, which adds to the cost of production.
US 2007/0092957 discloses synthesis of isobutanol by recombinant nonphotosynthetic bacteria and yeast that utilize glucose or sucrose as carbon sources. US 2007/0259411 describes the selection of butanol-tolerant bacterial Enterococcus species in a growth medium that includes a fermentable carbon source for the production of alcohols. US 2008/0261230 provides genes encoding high activity keto-acid reductoisomerases that can be used to genetically engineer microorganisms for the production of isobutanol. US 2009/0081746 discloses the synthesis of branched-chain alcohols including isobutanol, 1-butanol, 1-propanol, 2-methyl 1-butanol, 3-methyl-1-butanol, and 2-phenylethanol by recombinant E. coli strains in cultures that include glucose.
US 2009/0288337 (application Ser. No. 12/332,305) and WO 20009/076480 (PCT application US2008/086296), both incorporated by reference herein, describe genetically engineered microorganisms such as bacteria and yeast for the synthesis of 2-methyl-1-butanol.